Bài 24: MongoDB - Java(p2) - MongoDB

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1. Lấy tất cả document

Để chọn tất cả các document từ collection, phương thức find () của lớp com.mongodb.client.MongoCollection được sử dụng. Phương thức này trả về một con trỏ, vì vậy bạn cần phải lặp lại con trỏ này.
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.bson.Document;
import com.mongodb.MongoClient;
import com.mongodb.MongoCredential;
public class RetrievingAllDocuments {
	public static void main( String args[] ) {
	
		// Creating a Mongo client
		MongoClient mongo = new MongoClient( "localhost" , 27017 );
		
		// Creating Credentials
		MongoCredential credential;
		credential = MongoCredential.createCredential("sampleUser", "myDb", "password".toCharArray());
		System.out.println("Connected to the database successfully");
		
		// Accessing the database
		MongoDatabase database = mongo.getDatabase("myDb");
		
		// Retrieving a collection
		MongoCollection<Document> collection = database.getCollection("sampleCollection");
		System.out.println("Collection sampleCollection selected successfully");
		Document document1 = new Document("title", "MongoDB")
		.append("description", "database")
		.append("likes", 100)
		.append("url", "http://www.tutorialspoint.com/mongodb/")
		.append("by", "tutorials point");
		Document document2 = new Document("title", "RethinkDB")
		.append("description", "database")
		.append("likes", 200)
		.append("url", "http://www.tutorialspoint.com/rethinkdb/")
		.append("by", "tutorials point");
		List<Document> list = new ArrayList<Document>();
		list.add(document1);
		list.add(document2);
		collection.insertMany(list);
		// Getting the iterable object
		FindIterable<Document> iterDoc = collection.find();
		int i = 1;
		// Getting the iterator
		Iterator it = iterDoc.iterator();
		while (it.hasNext()) {
			System.out.println(it.next());
			i++;
		}
	}
}
Kết quả :
Connected to the database successfully
Collection sampleCollection selected successfully
Document{{_id=5dce4e9ff68a9c2449e197b2, title=MongoDB, description=database, likes=100, url=http://www.tutorialspoint.com/mongodb/, by=tutorials point}}
Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, likes=200, url=http://www.tutorialspoint.com/rethinkdb/, by=tutorials point}}

2. Cập nhật Document

Để cập nhật document từ collection, phương thức updateOne () của lớp com.mongodb.client.MongoCollection được sử dụng.
import com.mongodb.client.FindIterable; 
import com.mongodb.client.MongoCollection; 
import com.mongodb.client.MongoDatabase; 
import com.mongodb.client.model.Filters; 
import com.mongodb.client.model.Updates; 
import java.util.Iterator; 
import org.bson.Document;  
import com.mongodb.MongoClient; 
import com.mongodb.MongoCredential;  
public class UpdatingDocuments { 
   
   public static void main( String args[] ) {  
      
      // Creating a Mongo client 
      MongoClient mongo = new MongoClient( "localhost" , 27017 ); 
     
      // Creating Credentials 
      MongoCredential credential; 
      credential = MongoCredential.createCredential("sampleUser", "myDb", 
         "password".toCharArray()); 
      System.out.println("Connected to the database successfully");  
      
      // Accessing the database 
      MongoDatabase database = mongo.getDatabase("myDb"); 
      // Retrieving a collection 
      MongoCollection<Document> collection = database.getCollection("sampleCollection");
      System.out.println("Collection myCollection selected successfully"); 
      collection.updateOne(Filters.eq("title", 1), Updates.set("likes", 150));       
      System.out.println("Document update successfully...");  
      
      // Retrieving the documents after updation 
      // Getting the iterable object
      FindIterable<Document> iterDoc = collection.find(); 
      int i = 1; 
      // Getting the iterator 
      Iterator it = iterDoc.iterator(); 
      while (it.hasNext()) {  
         System.out.println(it.next());  
         i++; 
      }     
   }  
}
Kết quả như sau :
Connected to the database successfully
Collection myCollection selected successfully
Document update successfully...
Document{{_id=5dce4e9ff68a9c2449e197b2, title=MongoDB, description=database, likes=100, url=http://www.tutorialspoint.com/mongodb/, by=tutorials point}}
Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, likes=200, url=http://www.tutorialspoint.com/rethinkdb/, by=tutorials point}}

3. Xoá Document :

Để xóa document ra khỏi collection, bạn cần sử dụng phương thức deleteOne () của lớp com.mongodb.client.MongoCollection.
import com.mongodb.client.FindIterable; 
import com.mongodb.client.MongoCollection; 
import com.mongodb.client.MongoDatabase; 
import com.mongodb.client.model.Filters;  
import java.util.Iterator; 
import org.bson.Document; 
import com.mongodb.MongoClient; 
import com.mongodb.MongoCredential;  
public class DeletingDocuments { 
   
   public static void main( String args[] ) {  
   
      // Creating a Mongo client 
      MongoClient mongo = new MongoClient( "localhost" , 27017 );
      
      // Creating Credentials 
      MongoCredential credential; 
      credential = MongoCredential.createCredential("sampleUser", "myDb", 
         "password".toCharArray()); 
      System.out.println("Connected to the database successfully");  
      
      // Accessing the database 
      MongoDatabase database = mongo.getDatabase("myDb"); 
      // Retrieving a collection
      MongoCollection<Document> collection = database.getCollection("sampleCollection");
      System.out.println("Collection sampleCollection selected successfully"); 
      // Deleting the documents 
      collection.deleteOne(Filters.eq("title", "MongoDB")); 
      System.out.println("Document deleted successfully...");  
      
      // Retrieving the documents after updation 
      // Getting the iterable object 
      FindIterable<Document> iterDoc = collection.find(); 
      int i = 1; 
      // Getting the iterator 
      Iterator it = iterDoc.iterator(); 
      while (it.hasNext()) {  
         System.out.println(it.next());  
         i++; 
      }       
   } 
}
Kết quả :
Connected to the database successfully 
Collection sampleCollection selected successfully 
Document deleted successfully...
Document{{_id=5dce4e9ff68a9c2449e197b3, title=RethinkDB, description=database, likes=200, url=http://www.tutorialspoint.com/rethinkdb/, by=tutorials point}}

4. Loại bỏ Collection

Để loại bỏ một collection từ database, bạn cần sử dụng phương thức drop () của lớp com.mongodb.client.MongoCollection.
import com.mongodb.client.MongoCollection; 
import com.mongodb.client.MongoDatabase;  
import org.bson.Document;  
import com.mongodb.MongoClient; 
import com.mongodb.MongoCredential;  
public class DropingCollection { 
   
   public static void main( String args[] ) {  
      // Creating a Mongo client 
      MongoClient mongo = new MongoClient( "localhost" , 27017 ); 
      // Creating Credentials 
      MongoCredential credential; 
      credential = MongoCredential.createCredential("sampleUser", "myDb", 
         "password".toCharArray()); 
      System.out.println("Connected to the database successfully");  
      
      // Accessing the database 
      MongoDatabase database = mongo.getDatabase("myDb");  
      
      // Creating a collection 
      System.out.println("Collections created successfully"); 
      // Retrieving a collection
      MongoCollection<Document> collection = database.getCollection("sampleCollection");
      // Dropping a Collection 
      collection.drop(); 
      System.out.println("Collection dropped successfully");
   } 
}
Kết quả :
Connected to the database successfully 
Collection sampleCollection selected successfully 
Collection dropped successfully

5. Danh sách tất cả Collections

Để liệt kê tất cả các collection trong cơ sở dữ liệu, bạn cần sử dụng phương thức listCollectionNames () của lớp com.mongodb.client.MongoDatabase.
import com.mongodb.client.MongoDatabase; 
import com.mongodb.MongoClient; 
import com.mongodb.MongoCredential;  
public class ListOfCollection { 
   
   public static void main( String args[] ) {  
      
      // Creating a Mongo client 
      MongoClient mongo = new MongoClient( "localhost" , 27017 ); 
      // Creating Credentials 
      MongoCredential credential; 
      credential = MongoCredential.createCredential("sampleUser", "myDb", 
         "password".toCharArray()); 
      System.out.println("Connected to the database successfully");  
      
      // Accessing the database 
      MongoDatabase database = mongo.getDatabase("myDb"); 
      System.out.println("Collection created successfully"); 
      for (String name : database.listCollectionNames()) { 
         System.out.println(name); 
      } 
   }
}
Kết quả :
Connected to the database successfully 
Collection created successfully 
myCollection 
myCollection1 
myCollection5
Các phương thức MongoDB còn lại save (), limit (), bỏ qua (), sort (), v.v. hoạt động giống như được giải thích trong hướng dẫn tiếp theo.
Bài tiếp theo: MongoDB - PHP >>
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